Photon emission from hot hadronic matter described by an effective chiral Lagrangian

Song, Chungsik

doi:10.1103/physrevc.47.2861

Cited by 85 publications

(105 citation statements)

References 26 publications

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“…The hadron gas (HG) phase is modeled as an interacting meson gas within the SU(3) × SU(3) massive Yang-Mills approach used in previous studies (see, e.g., Refs. [12,31,32]). At tree level, this formalism contributes 8 photon-producing reaction channels involving π, K, ρ, ω, and a 1 mesons [33].…”

Section: Viscous Corrections To Thermal Photon Emission Ratesmentioning

confidence: 99%

“…(3) and collecting terms independent of and linear in π αβ , respectively. In the hadronic phase all internal propagators are massive, and we follow custom [31,32] by ignoring medium effects on the meson masses and coupling constants. π αβ corrections thus arise only from the explicit f (p) factors for the incoming and outgoing particles in Eq.…”

Section: Viscous Corrections To Thermal Photon Emission Ratesmentioning

confidence: 99%

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Anisotropic flow of thermal photons as a quark-gluon plasma viscometer

et al. 2015

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We present state-of-the-art calculations of viscous photon emission from nuclear collisions at RHIC and LHC. Fluctuating initial density profiles are evolved with event-by-event viscous hydrodynamics. Momentum spectra of thermal photons radiated by these explosively expanding fireballs and their pT -differential anisotropic flow coefficients vn(pT ) are computed, both with and without accounting for viscous corrections to the standard thermal emission rates. Viscous corrections to the rates are found to have a larger effect on the vn coefficients than the viscous suppression of hydrodynamic flow anisotropies. The benefits of taking the ratio of elliptic to triangular flow, v2/v3, are discussed, and the spacetime regions which contribute dominantly to the photon flow harmonics are identified. The directed flow v1 of thermal photons is predicted for RHIC and LHC energies.

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Section: Viscous Corrections To Thermal Photon Emission Ratesmentioning

confidence: 99%

Section: Viscous Corrections To Thermal Photon Emission Ratesmentioning

confidence: 99%

Anisotropic flow of thermal photons as a quark-gluon plasma viscometer

et al. 2015

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“…[28,29]. The obvious differences expected in a CFL phase are due to the different masses and strong couplings of the pions and rho mesons, as well as the modified pion dispersion relation.…”

Section: Emission Rates and Emissivitiesmentioning

confidence: 99%

“…As a check of our numerical calculation, we have ensured agreement with the results of Refs. [28,29] when using the vacuum values for masses (and velocities) of the pseudoscalar and vector mesons (pertinent curves for T = 50 MeV are displayed in the lower right panel of Fig. 1).…”

Section: Emission Rates and Emissivitiesmentioning

confidence: 99%

Photon emission from dense quark matter

2004

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Thermal emission rates and mean free paths of photons in a color-flavor locked (CFL) phase of quark matter at high densities and moderate temperatures are evaluated. Our calculations are based on a low-energy effective theory for CFL matter describing Goldstone boson excitations and their electromagnetic as well as strong interactions. Inmedium coupling strengths of vector mesons are estimated to be smaller than in vacuum. As a consequence of in-medium modified pion dispersion relations, novel processes such as π + π − → γ and γ → π + π − become possible. The total photon emissivity is found to be very large, exceeding contributions from thermal e + e − annihilation above temperatures of about 5 MeV. At the same time, the corresponding mean free paths become very small. Our results imply that the photon flux from the surface of a (hypothetical) CFL star in its early hot stages saturates the black-body limit. Schematic estimates for the early thermal evolution of the star are also presented.

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“…[2] we have calculated photon-generating processes including the exchange of a 1 , ρ, and π mesons within the massive Yang-Mills (MYM) approach [3,4], as well as the πρω vertex as given by the Wess-Zumino Lagrangian [5], augmented by standard (dipole) FFs [2,6] that are unity on-shell. The four parameters of the MYM Lagrangian can be fit using measured values [7] of m ρ , m a 1 , ρ→ππ , and a 1 →ρπ , whereas the coupling constant g ωπρ is fixed by the decay ω → πγ .…”

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confidence: 99%

Reply to “Comment on ‘Hadronic production of thermal photons’”

2005

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We address a recent comment by Alam et al. [Phys. Rev. C 71, 059802 (2005)], on our work of thermal photon emission rates from hadronic matter. Specifically, we explain how t-channel ω exchange in the πρ → πγ reaction arises as a dominant contribution to the rates at high energy and why hadronic form factors cannot be neglected in this assessment. [2], namely that t-channel ω exchange is a dominant source of high-energy photons from a thermal hadronic gas. In their reasoning, they intentionally omit the insertion of form factors (FFs) at hadronic vertices to "understand the relative importance of ω and a 1 exchange processes" [1].Hadronic FFs are a conventional way to incorporate finitesize effects in describing hadronic reactions, especially at high momentum transfer, where hadronic substructure becomes important. They arise naturally and are ubiquitous in field theories with emergent degrees of freedom. In Ref.[2] we have calculated photon-generating processes including the exchange of a 1 , ρ, and π mesons within the massive Yang-Mills (MYM) approach [3,4], as well as the πρω vertex as given by the Wess-Zumino Lagrangian [5], augmented by standard (dipole) FFs [2,6] that are unity on-shell. The four parameters of the MYM Lagrangian can be fit using measured values [7] of m ρ , m a 1 , ρ→ππ , and a 1 →ρπ , whereas the coupling constant g ωπρ is fixed by the decay ω → πγ . The latter is an off-shell decay (proceeding via an intermediate ρ meson) with the FF entering the decay width as ω→πγ ∝ (g ωπρ F F ωπρ ) 2 . We obtained g ωπρ = 22.6 GeV −1 (with a typical FF cutoff of 1 GeV), as compared to g ωπρ = 11.93 GeV −1 with F F ωπρ ≡ 1. The presence of the FF clearly and simply increases the coupling constant. Our procedure is corroborated by inspecting the triple-pion ω decay channel. In the gauged Wess-Zumino Lagrangian [5] that reproduces the radiative decay of the ω, the width for ω → πππ is ω→πππ = 5.1 MeV (with FF = 1), whereas the experimental result is 7.49 ± 0.08 MeV. Once the FF is implemented at each vertex of the reaction, we find ω→πππ = 7.47 MeV. The presence of the FF obviously increases the value of the coupling constant g ωπρ , but of course the full effect has to involve both coupling and FF. The net effect is an increase of the width for ω → πππ and this enhancement carries over to the π + ρ → π + γ reaction with ω exchange.As discussed in Ref.[2], for the case of ω exchange an incoherent addition of the s-and t-channel contributions is justified. This is illustrated in the top panel of

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Photon emission from hot hadronic matter described by an effective chiral Lagrangian

Cited by 85 publications

References 26 publications

Anisotropic flow of thermal photons as a quark-gluon plasma viscometer

Anisotropic flow of thermal photons as a quark-gluon plasma viscometer

Photon emission from dense quark matter

Reply to “Comment on ‘Hadronic production of thermal photons’”

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